Last glacial maximum deglaciation of the Southern Velebit Mt. (Croatia): insights from cosmogenic 36Cl dating of Rujanska Kosa

Abstract

Although several types of glacial landforms and deposits were described from different parts of the Croatian Dinarides, up to date there are no quantitative glacial chronological data. Here we present the first cosmogenic 36Cl glacial chronology from the Southern Velebit Mt. from a moraine complex known as the Rujanska Kosa. We sampled four limestone boulders and used 20 mm ka−1 erosion corrected ages, as the study area is composed of well-karstified carbonate deposits and located in one of the highest precipitation regions of Europe. The inner Rujanska Kosa ridge yielded an age of 20.7 ± 2.2 ka for the retreat of glaciers in that part of Velebit Mt. A slightly older age was measured from the outer ridge on the left-lateral part of the Rujanska Kosa, which dates back to 22.7 ± 2.7 ka ago. Whilst the ages between inner and outer ridges overlap within error, we can place an age difference between the two moraines to be between 0 and 6.9 ka, supported by the geomorphic evidence that the latter is older. Although we could not perform any geomorphological work higher up in the Rujno paleo-ice field due to the remnant minefields, our results may indicate a Late Pleistocene (i.e. la st glacial maximum) retreat of ice from the Southern Velebit Mt. Despite the small number of valid samples, acquired age data on glacial landforms in Southern Velebit Mt. are in accordance with ages from several other Mediterranean mountain ranges.